diff --git a/app/src/androidTest/java/org/isoron/uhabits/unit/models/RepetitionListTest.java b/app/src/androidTest/java/org/isoron/uhabits/unit/models/RepetitionListTest.java
index 1c30c28d0..173af0b51 100644
--- a/app/src/androidTest/java/org/isoron/uhabits/unit/models/RepetitionListTest.java
+++ b/app/src/androidTest/java/org/isoron/uhabits/unit/models/RepetitionListTest.java
@@ -61,7 +61,7 @@ public class RepetitionListTest
     }
 
     @Test
-    public void contains_testNonDailyHabit()
+    public void contains()
     {
         long current = DateHelper.getStartOfToday();
 
@@ -79,7 +79,7 @@ public class RepetitionListTest
     }
 
     @Test
-    public void delete_test()
+    public void delete()
     {
         long timestamp = DateHelper.getStartOfToday();
         assertThat(habit.repetitions.contains(timestamp), equalTo(true));
@@ -89,7 +89,7 @@ public class RepetitionListTest
     }
 
     @Test
-    public void toggle_test()
+    public void toggle()
     {
         long timestamp = DateHelper.getStartOfToday();
         assertThat(habit.repetitions.contains(timestamp), equalTo(true));
@@ -102,7 +102,7 @@ public class RepetitionListTest
     }
 
     @Test
-    public void getWeekDayFrequency_test()
+    public void getWeekDayFrequency()
     {
         Random random = new Random();
         Integer weekdayCount[][] = new Integer[12][7];
@@ -159,4 +159,16 @@ public class RepetitionListTest
         day.set(2015, 11, 1);
         assertThat(freq.get(day.getTimeInMillis()), equalTo(null));
     }
+
+    @Test
+    public void count()
+    {
+        long to = DateHelper.getStartOfToday();
+        long from = to - 9 * DateHelper.millisecondsInOneDay;
+        assertThat(habit.repetitions.count(from, to), equalTo(6));
+
+        to = DateHelper.getStartOfToday() - DateHelper.millisecondsInOneDay;
+        from = to - 5 * DateHelper.millisecondsInOneDay;
+        assertThat(habit.repetitions.count(from, to), equalTo(3));
+    }
 }
diff --git a/app/src/main/java/org/isoron/uhabits/models/Repetition.java b/app/src/main/java/org/isoron/uhabits/models/Repetition.java
index a2503706f..f43243698 100644
--- a/app/src/main/java/org/isoron/uhabits/models/Repetition.java
+++ b/app/src/main/java/org/isoron/uhabits/models/Repetition.java
@@ -26,10 +26,15 @@ import com.activeandroid.annotation.Table;
 @Table(name = "Repetitions")
 public class Repetition extends Model
 {
-
+    /**
+     * Habit to which this repetition belong.
+     */
     @Column(name = "habit")
     public Habit habit;
 
+    /**
+     * Timestamp of the day this repetition occurred. Time of day should be midnight (UTC).
+     */
     @Column(name = "timestamp")
     public Long timestamp;
 }
diff --git a/app/src/main/java/org/isoron/uhabits/models/RepetitionList.java b/app/src/main/java/org/isoron/uhabits/models/RepetitionList.java
index daa889669..c7b91351a 100644
--- a/app/src/main/java/org/isoron/uhabits/models/RepetitionList.java
+++ b/app/src/main/java/org/isoron/uhabits/models/RepetitionList.java
@@ -21,6 +21,8 @@ package org.isoron.uhabits.models;
 
 import android.database.Cursor;
 import android.database.sqlite.SQLiteDatabase;
+import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 
 import com.activeandroid.Cache;
 import com.activeandroid.query.Delete;
@@ -35,14 +37,15 @@ import java.util.HashMap;
 
 public class RepetitionList
 {
-
+    @NonNull
     private Habit habit;
 
-    public RepetitionList(Habit habit)
+    public RepetitionList(@NonNull Habit habit)
     {
         this.habit = habit;
     }
 
+    @NonNull
     protected From select()
     {
         return new Select().from(Repetition.class)
@@ -51,6 +54,7 @@ public class RepetitionList
                 .orderBy("timestamp");
     }
 
+    @NonNull
     protected From selectFromTo(long timeFrom, long timeTo)
     {
         return select().and("timestamp >= ?", timeFrom).and("timestamp <= ?", timeTo);
@@ -114,6 +118,7 @@ public class RepetitionList
      *
      * @return oldest repetition for the habit
      */
+    @Nullable
     public Repetition getOldest()
     {
         return (Repetition) select().limit(1).executeSingle();
@@ -129,6 +134,7 @@ public class RepetitionList
      *
      * @return total number of repetitions by month versus day of week
      */
+    @NonNull
     public HashMap<Long, Integer[]> getWeekdayFrequency()
     {
         Repetition oldestRep = getOldest();